---

private void jButtonActionPerformed(java.awt.event.ActionEvent evt) {
    try (BufferedReader br = new BufferedReader(new FileReader("class_progra"))) {
        DefaultTableModel dtm = (DefaultTableModel) jTable1.getModel();
        dtm.setRowCount(0);
        int rows = Integer.parseInt(br.readLine());
        
        for (int i = 0; i < rows; i++) {
            String surname = br.readLine();
            String name = br.readLine();
            String attendance = br.readLine();
            String mark = br.readLine();
            
            dtm.addRow(new Object[] {surname, name, attendance, mark});
        }
        jLabel1.setText("Added rows");
    } catch (IOException ex) {
        jLabel1.setText("Failed adding row");
    }
}